1. Field of the Invention
A special class of problems are present when utilizing electrical conductors for submersible power cable applications. In particular, with conventional oil well power cables it is often desirable to use stranded electrical conductors due to the increased flexibility thereof and the possibility of requiring multiple power paths. Due to the gaseous and liquid pressures created within well environments below ground, it is well known to require that the interstices between strands of a stranded electrical conductor to be filled with some type of insulating filler material to prevent the internal flow of fluid axially therethrough from motors or other power utilizing devices. Therefore in order to prevent the axial flow of fluids, a completely void-free filling material must be placed in the interstices between strands of the stranded electrical conductor to completely fill the space inside of the primary external dielectric insulation.
The primary external conductor insulation must withstand being exposed to environments having various corrosive and destructive characteristics such as wide variations in temperatures and exposure to a wide variety of chemicals as well as high axial pressures.
The present invention provides a means for applying the filling insulation in the interstices between strands of the stranded electrical conductor and providing a primary external electrical insulation on the conductor by utilizing a single step of overwrapping followed by a single step of heat shrinking. By utilizing two such simple steps the entirely void-free electrically insulated conductor is formed.
2. Description of the Prior Art
It is well known to form a layer of electrical insulation about the external surface of a stranded electrical conductor. It is similarly well known to fill the interstices between adjacent strands of a stranded electrical conductor with a filling insulation means. Such well known processes and constructions are shown or suggested in the disclosures of the following U.S. Pat. Nos.: 2,438,956; 2,718,544; 2,995,616; 3,223,773; 3,525,798; 3,576,387; 3,609,207; 3,624,594; 3,681,510; 3,691,505; 3,708,611; 3,710,007; 3,733,427; 3,758,353; 3,775,548; 3,812,283; 3,847,694; 3,891,790; 3,957,382; 3,995,964.
Particularly the '387 patent shows a laminated tube utilizing a heat shrinkable plastic outer shell and a plastic inner shell containing conductive metallic elements. Therefore this patent discloses the heat shrinkable outer insulation means. Other patents such as U.S. Pat. No. 2,438,956 show the use of a soft insulating material between individual stranded elements of a stranded electrical conductor.
None of these patents shows the construction of a final cable configuration with a filling insulation and a primary external insulation of different materials wherein a single step of tape overwrapping followed by a single step of heating achieves the final desired structure. Similarly none of these patents shows the use of a laminated tape formed of two components wherein the inner component comprises the filler insulation and the outer component comprises the primary dielectric insulation.